A grim location for a wake (6)

I believe the answer is:

astern

I'm a little stuck... Click here to teach me more about this clue!

'location for a wake' is the definition.
I can't tell whether this definition defines the answer.

'a grim' is the wordplay.
'grim' becomes 'stern' (synonyms).
'a'+'stern'='ASTERN'

Can you help me to learn more?

(Other definitions for astern that I've seen before include "Behind (naut.)" , "Towards the back (of a ship)" , "Aft" , "Toward the back of a boat" , "at the vessel's rear" .)

I've seen this clue in The Independent.

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